High speed low power multiple standard and supply output driver

Abstract

A multi-mode driver and method therefore includes a plurality of amplifiers, an adjustable load block, and adjustable current supply circuitry that selectively adjusts current magnitudes supplied to at least one of the plurality of amplifiers. The multi-mode driver can operate in a KR mode with a higher voltage supply, an SR4 mode with the higher voltage supply, and an SFI mode with a lower voltage supply. To support these modes, the multi-mode driver selectively operates a plurality of amplifiers, adjusts current magnitudes supplied to the amplifiers, and selectively adjusts an adjustable load. Thus, the multi-mode driver is operable to selectively and efficiently produce high swing and low swing output signals and to efficiently operate with any one of a plurality of supplies. The driver includes selectable loads and parallel-coupled amplifier devices that are selected based on mode.

1. A multi-mode driver, comprising:
 a two-stage adjustable load further including:
 a first stage that includes a plurality of selectable signal paths; 
 a second stage coupled to the first stage that includes at least one resistive element; and 
 wherein a total resistance of the two-stage adjustable load is based upon a selected signal path of the first stage and the at least one resistive element of the second stage; 
 
 first and second amplifiers coupled to an output of the two-stage adjustable load wherein at least one of the first and second amplifiers is selectable; and 
 load selection logic for selecting at least one of the plurality of selectable signal paths and at least one of the first and second amplifiers based upon whether a mode of operation of the multi-mode driver is one of a high swing mode, a low swing mode or an idle mode and based upon a supply voltage level. 
 
     
     
       2. The multi-mode driver of  claim 1  wherein the driver is configured to:
 place the first and second selectable amplifiers in the reduced power mode during the idle mode; 
 select the first amplifier for operation during the low swing mode and leave the second selectable amplifier in a reduced power mode; and 
 select both the first and second amplifiers for operation during the high swing mode. 
 
     
     
       3. The multi-mode driver of  claim 1  further including gate bias voltage selecting logic for selecting an activation voltage of a plurality of MOSFET switch devices based upon whether the driver is in the low swing or the high swing mode of operation. 
     
     
       4. The multi-mode driver of  claim 1  further including gate bias voltage selecting logic for selecting an activation voltage of a plurality of MOSFET switch devices based upon the supply voltage level. 
     
     
       5. The multi-mode driver of  claim 1  further including current scaling logic to scale an amplifier current level of the first and second selectable amplifiers based upon the mode of operation. 
     
     
       6. The multi-mode driver of  claim 5  further including selectable current sources for the first and second amplifiers to reduce power consumption based on the mode of operation. 
     
     
       7. The multi-mode driver of  claim 1  wherein the first and second amplifiers are differential amplifiers having differential outputs and wherein the second stage of the adjustable load comprises a pair of calibrated resistive elements, coupled to the differential outputs of the first and second amplifiers. 
     
     
       8. The multi-mode driver of  claim 1  wherein the multi-mode driver maintains a substantially constant common mode voltage at an output of the multi-mode driver when transitioning from one of the low swing mode or the high swing mode to the idle mode. 
     
     
       9. The multi-mode driver of  claim 1  wherein the plurality of selectable signal paths comprises:
 a first selectable signal path further including a calibrated resistor for operation in the low swing mode of operation when the supply voltage is a first supply voltage level; 
 a second selectable signal path for operation:
 in the high swing mode of operation when the supply voltage is at the first supply voltage level; and 
 in the low swing mode of operation when the supply voltage is at a second supply voltage level which is lower than the first supply voltage level; 
 
 a third selectable path for operation in the idle mode of operation; and 
 a gate bias selecting logic for selectively applying an activation voltage across a gate terminal to avoid over-voltage based on a mode of operation and the supply voltage level. 
 
     
     
       10. A multi-mode driver, comprising:
 a plurality of selectable signal paths in an adjustable load; 
 circuitry operable to selecting one of the plurality of selectable signal paths based upon at least one of whether:
 the multi-mode driver is operating in one of a high swing mode, a low swing mode or an idle mode of operation; and 
 a supply voltage level is a first voltage level or a second voltage level; 
 
 a plurality of selectable amplifiers; and 
 circuitry operable to selecting one of the plurality of selectable amplifiers based upon whether the multi-mode driver is operating in one of a high swing mode, a low swing mode or an idle mode of operation. 
 
     
     
       11. The multi-mode driver of  claim 10  wherein the multi-mode driver selects a first selectable signal path of the selectable load when:
 the mode of operation is the low swing mode and the supply voltage is the first voltage level. 
 
     
     
       12. The multi-mode driver of  claim 10  wherein the multi-mode driver selects a second selectable signal path when:
 the mode of operation is the high swing mode and the supply voltage is the first voltage level; and 
 the mode of operation is the low swing mode and the supply voltage is the second voltage level. 
 
     
     
       13. The multi-mode driver of  claim 12  wherein the second voltage level of the supply voltage is a lower magnitude voltage level than the first voltage level. 
     
     
       14. The multi-mode driver of  claim 12  wherein the multi-mode driver selects a third selectable signal path when:
 the mode of operation is the idle mode of operation. 
 
     
     
       15. A method in a multi-mode driver, comprising:
 determining whether a supply is producing a first or a second voltage level; 
 determining if a mode of operation for a multi-mode driver is a high swing mode or a low swing mode; 
 selecting a first signal path of an adjustable load having a first calibrated resistive element when the determined mode of operation is the low swing mode and the supply is producing the first voltage level; 
 selecting a second signal path of the adjustable load when the determined mode of operation is the low swing mode and the supply is producing the second voltage level; 
 selecting the second signal path of the adjustable load when determined mode of operation is the high swing mode and the supply is producing the first voltage level; 
 selecting a first of a plurality of amplifiers for operation when the mode of operation is a low swing mode; and 
 selecting the first and a second of the plurality of amplifiers for operation when the mode of operation is the high swing mode. 
 
     
     
       16. The method of  claim 15  further including selecting a third signal path of the adjustable load when the mode of operation is an idle mode of operation and maintaining an activation or bias level for at least one device that is the same as the activation or bias level from a preceding mode of operation. 
     
     
       17. The method of  claim 16  further including decoupling a selectable current source for each of the plurality of amplifiers when in the idle mode of operation. 
     
     
       18. The method of  claim 15  further including turning off the second of the plurality of amplifiers when in operating in the low swing mode. 
     
     
       19. The method of  claim 15  further including selecting a gate bias or activation voltage of a plurality of MOSFET switch devices operably disposed within at least one of the adjustable load and the plurality of amplifiers based upon whether the multi-mode driver is operating in the high swing mode or the low swing mode. 
     
     
       20. The method of  claim 15  further including selecting the gate bias or activation voltage of the plurality of MOSFET switch devices based upon whether the supply is producing the first or the second voltage level. 
     
     
       21. The method of  claim 15  further including substantially maintaining a common mode voltage level after transitioning from the high swing mode to the idle mode. 
     
     
       22. The method of  claim 15  further including substantially maintaining a common mode voltage level after transitioning from the low swing mode to the idle mode. 
     
     
       23. A multi-mode driver, comprising:
 a plurality of amplifiers; 
 an adjustable load that defines a plurality of load signal paths coupled between the plurality of amplifiers and a supply; 
 adjustable current supply circuitry that selectively adjusts current magnitudes supplied to at least one of the plurality of amplifiers; and 
 wherein the multi-mode driver is operable to support operations in one of a plurality of driver modes of operation by selecting at least one of a plurality of amplifiers to adjust the supplied current magnitudes, by selecting or coupling to one of a higher magnitude or lower magnitude voltage supply level, and by selecting at least one of a plurality of load signal paths. 
 
     
     
       24. The multi-mode driver of  claim 23 , wherein, when operating in an idle mode of operation, the multi-mode driver maintains a common mode voltage level at an output of the multi-mode driver. 
     
     
       25. The multi-mode driver of  claim 23  wherein, when operating in an idle mode of operation, the multi-mode driver places each of the plurality of amplifiers in a low current mode of operation. 
     
     
       26. The multi-mode driver of  claim 23  configured to operate in a KR mode of operation wherein, when operating in a KR mode with a higher voltage supply, the multi-mode driver selects at least two of the plurality of amplifiers for operation, selects at least one selectable current source, selects a signal path to increase a supply level, and produces a high swing output. 
     
     
       27. The multi-mode driver of  claim 23  configured to operate in an SR4 mode of operation, wherein, when operating in an SR4 with a higher voltage supply, the multi-mode driver selects a first amplifier for operation and at least one selectable current source and selectively places a second amplifier in a reduced current mode and deselects at least one current source, selects a signal path to maximize a resistive load magnitude of the adjustable load to prevent over-voltage, and produces a low swing output. 
     
     
       28. The multi-mode driver of  claim 27  wherein, when operating in the SR4 mode, the reduced current mode for the second amplifier is no current and the multi-mode driver turns off the second amplifier. 
     
     
       29. The multi-mode driver of  claim 23  configured to operate in an SFI mode of operation, wherein, when operating in an SFI with a lower voltage supply, selects a first amplifier for operation and at least one selectable current source and selectively places a second amplifier in a reduced current mode and deselects at least one current source, selects a signal path to increase the supply level, and produces a low swing output. 
     
     
       30. The multi-mode driver of  claim 29  wherein, when operating in the SFI mode, the reduced current mode for the second amplifier is no current and the multi-mode driver turns off the second amplifier.